A multidisciplinary effort has been initiated to develop (a) an antineoplastic agent effective against slow growing tumors, and (b) a radiosensitizing agent to selectively sensitize hypoxic tumor cells towards treatment with X-irradiation. Butylated hydroxytoluene (BHT) and its analogs represent a class of agents that are free radical inhibitors and have been shown to inhibit enzymatic redox processes and protein biosynthesis in tumor cells. Appropriate chemical modifications of BHT will be made to provide an agent with greater potential for clinical utility than BHT as an antineoplastic agent specifically against slow growing tumors. Gold triphenylphosphine complex of thymidine has been shown to possess antineoplastic activity. A series of gold complexes of various nucleosides will be synthesized in an attempt to obtain an agent which may possess activity against solid tumors. The relative radioresistance of hypoxic cells present in tumors is a critical limitation to the successful radiotherapy of cancer in man. Development of chemical sensitizers has been undertaken to overcome this problem. An extensive structure activity relationship study has been initiated for nitroimidazole analogs to explore the relationship between electron affinity and radiosensitization. A variety of analogs of 2- and 5-nitroimidazole will be synthesized and tested for radiosensitization by in vitro and in vivo techniques.